Hubble's constant, the age of the universe
and the consequences of unbridled expansion
Using Hubble’s discoveries to calculate the age of the universe
When stars in distant galaxies recede from us, we can observe a shift towards the red in the spectra of light reaching us from them. The principle involved is similar to the Doppler effect: the sound of a police siren is higher in pitch when the vehicle bearing the siren is moving towards you, and lower in pitch as it moves away [0]. By observing a distant galaxy’s red shift factor (see illustration below) as it moves away and using Hubble’s constant (presently calculated to be around 72 km (45 miles)/ sec per 3.26 million light years[1]), scientists can calculate the rate at which and for how long it has been doing so. By reversing the process back to the big bang, they can calculate the approximate age of the universe, which is presently estimated to be 13.73 billion years old.[2]. As Michael S Turner succinctly puts it: “It is Hubble’s law, played back in time, that points to a big bang 13.7 billion years ago”[3]
For objects moving away from the Earth, the result is red shifted (right).
Whereas, for objects moving towards the earth (eg the Andromeda galaxy), it is blue shifted (below):
Source: http://astronomy.swin.edu.au/sao/downloads/HET603-M05A01.pdf: Colours and Spectral Types: Learning about stars from their spectra”.
[0] Gavin Hesketh, The Particle Zoo - The search for the fundamental nature of reality, Quercus, Hachette, London, 2016, 230.
[1] Hubble’s initial calculation value was around 500 km (300 miles)/sec per 3.26 million light years, which seemed to indicate that the Universe was younger than the earth: Adam Hart-Davis, Science – The Definitive Visual Guide, London, 2009, p 319 - a result which Lawrence Krauss describes as ‘embarrassing for scientists’. “More important, it suggests something is wrong with the analysis”: Lawrence M. Krauss, A Universe from Nothing – Why there is something rather than nothing, Free Press, New York, 2012, p 15.
[2] Gleiser, 73; Chris LaRocco and Blair Rothstein: The Big Bang, op cit. See also ‘Universe aged 13 billion years’, SMH, 25 April 2002. On Hubble’s constant, see also David Christian, Maps of Time, op cit (2011), 31-32.
[3] Origin of the Universe, op cit, at 38.
[0] Gavin Hesketh, The Particle Zoo - The search for the fundamental nature of reality, Quercus, Hachette, London, 2016, 230.
[1] Hubble’s initial calculation value was around 500 km (300 miles)/sec per 3.26 million light years, which seemed to indicate that the Universe was younger than the earth: Adam Hart-Davis, Science – The Definitive Visual Guide, London, 2009, p 319 - a result which Lawrence Krauss describes as ‘embarrassing for scientists’. “More important, it suggests something is wrong with the analysis”: Lawrence M. Krauss, A Universe from Nothing – Why there is something rather than nothing, Free Press, New York, 2012, p 15.
[2] Gleiser, 73; Chris LaRocco and Blair Rothstein: The Big Bang, op cit. See also ‘Universe aged 13 billion years’, SMH, 25 April 2002. On Hubble’s constant, see also David Christian, Maps of Time, op cit (2011), 31-32.
[3] Origin of the Universe, op cit, at 38.
The expansionary principle is illustrated below:
Source: Michael S Turner, “Origin of the Universe”, Scientific American: Special Collector’s Edition: Extreme Physics, Probing the Mysteries of the Cosmos, August 2013, 39
And in somewhat different fashion here:
And in somewhat different fashion here:
Source: Adam Hart-Davis, Science – The Definitive Visual Guide, DK, London, 2009, p 319.
Corroboration of Hubble’s constant and the consequences of unbridled expansion
The uncertainty range of ± 0.11 Ga governing the expansion rate of Hubble’s constant referred to several pages back and the date of 13.73 billion years itself has been obtained by the agreement of a number of other scientific research projects, such as microwave background radiation measurements by the Wilkinson Microwave Anisotropy Probe (WMAP) released by NASA in February 2003 and other probes. The WMAP, launched in June 2001, was sent out to a distance of one million miles from earth where on the far side of the Earth from the Sun, it could view the microwave without contamination from sunlight. Measurements of the cosmic background radiation give the cooling time of the universe since the big bang, and measurements of the expansion rate of the universe can be used in conjunction to calculate its approximate age by extrapolating backwards in time[1].
However, there has recently emerged a discrepancy between the rate of the universe’s expansion (the Hubble constant or H0) as measured by two distinct methodologies. One method involves using light left over from shortly after the big bang and looking forward to the present day. By utilising the overdensities and underdensities of matter imprinted on the CMB as minor temperature variations, scientists are able to use them as a "standard ruler" against which to chart the universe's subsequent growth and evolution.
The other method, looking back from the present, utilises rungs in the cosmic distance ladder to do the measurement. The first rung are so-called Cepheid variables, Cepheid stars of variable brightness first of all in the Milky Way, then Cepheids and type 1a Supernovae in a nearby galaxy based on the first-rung calculations and then type 1a Supernovae in distant galaxies based on second-rung calculations.
Suffice it to say that there is a discrepancy in the results of the two modes of calculation. The CMB early universe value for H0 is 67 (in units of kms per second per 3.26 million light-years). The Cepheid-based, late universe value is 74. A new alternative to Cepheids – red giant stars that flare with a known intrinsic brightness – comes up with a value between the two being an H0 of about 70, only serving to complicate the tensions between the first and second methodologies. If these discrepancies are incapable of being reconciled, scientists may need to look beyond the Standard Cosmological Model to a so-called "new physics"' to provide the answer [1.1].
On another aspect, by using standard principles of nuclear theory and thermodynamics, scientists have also calculated that about 23% of the universe should be composed of helium, and in 1995, NASA scientists were able to detect primordial helium in the far reaches of the universe, a finding consistent with an important aspect of the big bang theory that a mixture of hydrogen and helium was created when the universe began, but ceased within a few hours of the big bang[2].
Consequences of unbridled expansion
The rate of spatial expanse (which is relevant only on the largest of cosmic scales and has no direct impact on smaller entities like individual galaxies or our solar system, where ordinary attractive gravity still reigns) is becoming so enormous that the region we are able to see, even with the aid of the most powerful telescope possible, is but a tiny fraction of the whole universe. None of the light emitted from the vast majority of the universe could have reached us yet, and much of it won’t arrive until long after the sun and the earth have died out, and if the entire cosmos were scaled down to the size of the earth, the part accessible to us would be much smaller than a grain of sand[3].
In 2004, the Hubble Ultra Deep Field image showed the oldest galaxies ever seen – an estimated 10,000 galaxies total in the field of view, with some having emitted their light about 13 billion years ago, round about the time the universe came into existence. The light Hubble is receiving today (2005) left such systems some 8.5 billion years before the Earth was even formed![4] The reason that these images can be seen at all is that the light, travelling a constant speed across great distances involving billions of miles and millions of light years, takes so long to get here so we are presently observing what went on billions of years ago. Even as we look at the stars above with the naked eye, the light we see is already cosmic light years old. We are in fact looking into the past[5].
To give some idea of the scales involved, when we look at the Andromeda galaxy the light we receive was emitted some 3 million years ago. But when we look at the Coma cluster, the light we receive was emitted 300 million years ago, and if right now, all the stars in all the galaxies in this cluster were to go supernova (violently explode), we would still see the same undisturbed image of the Coma cluster and would do so for another 300 million years. Conversely, should an astronomer in the Coma cluster now turn a superpowerful telescope towards earth, he or she would see an abundance of ferns, anthropods and early reptiles in our neighbourhood and would have no view of the Great Wall of China or the Eiffel Tower for another 300 million years.
About a hundred billion years from now, all but the closest of galaxies will be dragged away by the swelling space at faster-than-light speed and so would be impossible for us to see, regardless of the power of telescopes used. Michael S Turner envisages an even earlier scenario, commenting that in 30 billion years or so, all traces of the big bang will have disappeared; the light from all but a handful of nearby galaxies will be too redshifted to detect; the temperature of the CMBR will be too low to measure; and the universe will be similar to one that astronomers knew 100 years ago before their instruments were powerful enough to reveal the universe we know today[6]. If these ideas are correct, then in the far future, the universe will be a vast, empty and lonely place.[7]
The Coma cluster, incidentally, is one of those diffuse, difficult-to- detect, ‘skim milk’ galaxies suspected of being failed Milky Ways – “big galaxies that were headed for brilliance but (which) lost their gas before forming many stars, perhaps because supernova explosions catapulted gas out of the galaxies and into the parent Coma cluster. They must also harbor lots of dark matter to hold together; otherwise the gravitational pull of other galaxies in the cluster would rip them apart”. How much dark matter they possess is unknown because no one has yet been able to measure their mass[8].
[1] http://en.wikipedia.org/wiki/Age_of_the_universe See also David Christian, op cit (2011) 34, 516; Lawrence M. Krauss, A Universe from Nothing – Why there is something rather than nothing, Free Press, New York, 2012, 87.
[1.1] The issues are explored in an article by Richard Panek entitled “A Cosmic Crisis”, Scientific American, March 2020, 22-29.
[2] Chris LaRocco and Blair Rothstein: The Big Bang, op cit. See also Greene, Elegant Universe, (2000), 349, Hawking 319, and below under the heading “The discovery of dark matter in the 19602”.
[3] Source for this and the material which follows: Greene (2005), 285, and Chapter 10 of Fabric of the Cosmos (2005).
[4] Ibid, 69
[5] Greene (2011), 41.
[6] Ibid, 43, “In the Dark”.
[7] Source: Greene (2005), 301.
[8] Ken Crosswell, Galactic Ghosts”, Scientific American, April 2015, 17.
Corroboration of Hubble’s constant and the consequences of unbridled expansion
The uncertainty range of ± 0.11 Ga governing the expansion rate of Hubble’s constant referred to several pages back and the date of 13.73 billion years itself has been obtained by the agreement of a number of other scientific research projects, such as microwave background radiation measurements by the Wilkinson Microwave Anisotropy Probe (WMAP) released by NASA in February 2003 and other probes. The WMAP, launched in June 2001, was sent out to a distance of one million miles from earth where on the far side of the Earth from the Sun, it could view the microwave without contamination from sunlight. Measurements of the cosmic background radiation give the cooling time of the universe since the big bang, and measurements of the expansion rate of the universe can be used in conjunction to calculate its approximate age by extrapolating backwards in time[1].
However, there has recently emerged a discrepancy between the rate of the universe’s expansion (the Hubble constant or H0) as measured by two distinct methodologies. One method involves using light left over from shortly after the big bang and looking forward to the present day. By utilising the overdensities and underdensities of matter imprinted on the CMB as minor temperature variations, scientists are able to use them as a "standard ruler" against which to chart the universe's subsequent growth and evolution.
The other method, looking back from the present, utilises rungs in the cosmic distance ladder to do the measurement. The first rung are so-called Cepheid variables, Cepheid stars of variable brightness first of all in the Milky Way, then Cepheids and type 1a Supernovae in a nearby galaxy based on the first-rung calculations and then type 1a Supernovae in distant galaxies based on second-rung calculations.
Suffice it to say that there is a discrepancy in the results of the two modes of calculation. The CMB early universe value for H0 is 67 (in units of kms per second per 3.26 million light-years). The Cepheid-based, late universe value is 74. A new alternative to Cepheids – red giant stars that flare with a known intrinsic brightness – comes up with a value between the two being an H0 of about 70, only serving to complicate the tensions between the first and second methodologies. If these discrepancies are incapable of being reconciled, scientists may need to look beyond the Standard Cosmological Model to a so-called "new physics"' to provide the answer [1.1].
On another aspect, by using standard principles of nuclear theory and thermodynamics, scientists have also calculated that about 23% of the universe should be composed of helium, and in 1995, NASA scientists were able to detect primordial helium in the far reaches of the universe, a finding consistent with an important aspect of the big bang theory that a mixture of hydrogen and helium was created when the universe began, but ceased within a few hours of the big bang[2].
Consequences of unbridled expansion
The rate of spatial expanse (which is relevant only on the largest of cosmic scales and has no direct impact on smaller entities like individual galaxies or our solar system, where ordinary attractive gravity still reigns) is becoming so enormous that the region we are able to see, even with the aid of the most powerful telescope possible, is but a tiny fraction of the whole universe. None of the light emitted from the vast majority of the universe could have reached us yet, and much of it won’t arrive until long after the sun and the earth have died out, and if the entire cosmos were scaled down to the size of the earth, the part accessible to us would be much smaller than a grain of sand[3].
In 2004, the Hubble Ultra Deep Field image showed the oldest galaxies ever seen – an estimated 10,000 galaxies total in the field of view, with some having emitted their light about 13 billion years ago, round about the time the universe came into existence. The light Hubble is receiving today (2005) left such systems some 8.5 billion years before the Earth was even formed![4] The reason that these images can be seen at all is that the light, travelling a constant speed across great distances involving billions of miles and millions of light years, takes so long to get here so we are presently observing what went on billions of years ago. Even as we look at the stars above with the naked eye, the light we see is already cosmic light years old. We are in fact looking into the past[5].
To give some idea of the scales involved, when we look at the Andromeda galaxy the light we receive was emitted some 3 million years ago. But when we look at the Coma cluster, the light we receive was emitted 300 million years ago, and if right now, all the stars in all the galaxies in this cluster were to go supernova (violently explode), we would still see the same undisturbed image of the Coma cluster and would do so for another 300 million years. Conversely, should an astronomer in the Coma cluster now turn a superpowerful telescope towards earth, he or she would see an abundance of ferns, anthropods and early reptiles in our neighbourhood and would have no view of the Great Wall of China or the Eiffel Tower for another 300 million years.
About a hundred billion years from now, all but the closest of galaxies will be dragged away by the swelling space at faster-than-light speed and so would be impossible for us to see, regardless of the power of telescopes used. Michael S Turner envisages an even earlier scenario, commenting that in 30 billion years or so, all traces of the big bang will have disappeared; the light from all but a handful of nearby galaxies will be too redshifted to detect; the temperature of the CMBR will be too low to measure; and the universe will be similar to one that astronomers knew 100 years ago before their instruments were powerful enough to reveal the universe we know today[6]. If these ideas are correct, then in the far future, the universe will be a vast, empty and lonely place.[7]
The Coma cluster, incidentally, is one of those diffuse, difficult-to- detect, ‘skim milk’ galaxies suspected of being failed Milky Ways – “big galaxies that were headed for brilliance but (which) lost their gas before forming many stars, perhaps because supernova explosions catapulted gas out of the galaxies and into the parent Coma cluster. They must also harbor lots of dark matter to hold together; otherwise the gravitational pull of other galaxies in the cluster would rip them apart”. How much dark matter they possess is unknown because no one has yet been able to measure their mass[8].
[1] http://en.wikipedia.org/wiki/Age_of_the_universe See also David Christian, op cit (2011) 34, 516; Lawrence M. Krauss, A Universe from Nothing – Why there is something rather than nothing, Free Press, New York, 2012, 87.
[1.1] The issues are explored in an article by Richard Panek entitled “A Cosmic Crisis”, Scientific American, March 2020, 22-29.
[2] Chris LaRocco and Blair Rothstein: The Big Bang, op cit. See also Greene, Elegant Universe, (2000), 349, Hawking 319, and below under the heading “The discovery of dark matter in the 19602”.
[3] Source for this and the material which follows: Greene (2005), 285, and Chapter 10 of Fabric of the Cosmos (2005).
[4] Ibid, 69
[5] Greene (2011), 41.
[6] Ibid, 43, “In the Dark”.
[7] Source: Greene (2005), 301.
[8] Ken Crosswell, Galactic Ghosts”, Scientific American, April 2015, 17.