Our own universe may be but one bubble of space-time in a much bigger multiverse.
Credit: Greg Smye-Rumsby
This article is an edited extract of the book From Here to Infinity: The Royal Observatories Greenwich Guide to Astronomy, published by the University of Western Australia Press.
Credit: University of Western Australia Press
Edwin Hubble made the two most important discoveries in cosmology. First, he proved that many nebulae are other "island universes" or galaxies, beyond the boundaries of the Milky Way.
Then, working alongside colleagues at the Mount Wilson Observatory, he discovered that these galaxies are moving apart from one another – in effect that the universe is expanding.
In the second half of the 1920s, Hubble was still primarily interested in measuring the distances to galaxies. He was intrigued by a discovery that had been made in the previous decade by Vesto Slipher, an astronomer working at the Lowell Observatory in Flagstaff, Arizona.
Slipher had been working with a 24-inch (61-cm) refracting telescope that had a new instrument called a spectrograph attached to it. This could make photographs of the spectra of faint astronomical objects, by adding up the light over several nights if necessary. Among the objects Slipher studied in this way were several of the family then still known as nebulae, which Hubble was about to prove were actually external galaxies.
By 1925, just when Hubble was beginning to measure distances to galaxies, Slipher had measured 41 of these spectra, and found that just two of them (including the Andromeda Nebula) showed blueshifts, while 39 showed redshifts. This was the limit of what he could do with the 24-inch telescope, but the evidence hinted that the galaxies that looked bigger and brighter had smaller redshifts.
The obvious inference was that galaxies that look bigger and brighter are closer to us – so Hubble guessed that measuring redshifts might be a way of measuring distances to galaxies, and roped in his co-worker Milson Humason to test the idea with the 100-inch (250-cm) telescope. Humason measured the redshifts, while Hubble estimated the distances to the same galaxies using other methods.
THE REDSHIFT
By the beginning of the 1930s, Hubble and Humason had made enough observations to show that the relationship between redshift and distance is about as straightforward as it could possibly be: the redshift is proportional to the distance – or, putting it the way round that mattered to Hubble, distance is proportional to redshift.
This is now known as Hubble's Law. It means that if one galaxy has twice the redshift of another it is twice as far away, and so on. Once the distances to a few nearby galaxies had been measured by other means, the rule could be calibrated, and distances to other galaxies, much farther away across the universe, could be measured simply by measuring their redshifts.
In fact, this simple law only applies accurately to relatively nearby galaxies, and a more subtle relationship applies farther out across the universe, but this does not detract from the importance of Hubble's discovery.
Hubble himself was not interested in why the light from galaxies showed redshifts. All he cared about was how the redshift (whatever its cause) could be used to measure distances. But the natural guess people made at first was that the redshifts are caused by the Doppler effect.
If so, it meant that just two external galaxies (including Andromeda) are moving towards us, and all the rest are moving away – not as individuals, but as members of clusters like the Virgo Cluster. It was soon realised, however, that this recession of the galaxies is not caused by galaxies and clusters moving through space.
Albert Einstein's general theory of relativity, which he had completed in 1915, described how space itself could be bent by the presence of matter, like a stretched rubber sheet with a heavy weight on it. The equations also described how space as a whole could stretch, but in 1915 nebulae hadn't even been identified as external galaxies, and Einstein had dismissed this as a trick of the mathematics with no physical significance.
The shape of the universe
Regarding the way we see the shape of the universe,"open","closed","flat".Maybe it's possible that there are other geometries,just not avilable to the common eye.Of course this point does spill over into 'religion',but maybe for to long now we have been seeing the universe through scientific blinkers. Maybe there is a need to take a more "holistic" view?
Excellent science writing
Thanks to John Gribbon for laying out all these ideas with exceptional clarity.
Fussing with Religion...
We spend too much effort trying to 'stand' in the middle of this issue and keeping science, philosophy, and religion apart. Frankly, isn't it the truth we seek regardless of those three subjects? And regardless of where it points? What I find strange is that (we) scientists and philosophers do not consider God! I mean after all, we are in three dimensions that we are comfortable with; length, width and depth...and then one that is just a pest and seems to be broken (goes only one way)--time. Why not consider more dimensions--say up to about ten or eleven? Is anyone trying to scientifically investigate this?
Now that we know that time, space, matter and energy 'began' at the singularity...in which George Lemaitre called the "primordial egg" (and by which Holye then ridiculed him labeling it a "Big Bang"...which stuck), it all does seem rather like a Genesis event.... I admit having God enter this (and be responsible for it) bothers many of us but honestly...why should it? And how would one dodge this Bullet (which smacks of Pascal's Wager)? We are stuck in this life (existence) through no choice of our own; floating down a 'river' of time and all the while entropy is slowly sapping the energy out of us...we see the falls ahead and we are all going over them to our end (or could it be our beginning...back 'Home' where we all came from in the first place)? What if God was like the author of a book who develops a plot from outside of the cover and pages and ink? What if the medium by which an author inputs his information (the pages and ink) is there only as a communications medium to transmit and transcend the information outward to the reader? We know that it is not the ink or paper which is intelligent--it is rather the information that transcended the ink and paper which points beyond itself to an intelligence which is (again) beyond the medium...and reveals the plot. Is the message that goes through a telephone wire (or cell-phone satellite transmission) the actual intelligence? No! The information that comes to the listener points to the intelligence of a speaker...who made/placed the call. Why cannot this be nearly the same thing in that God transmits information in the design of the Creation in a way that gets our attention causing us to ask "why" (about too many things!)? Further, if this can be entertained it then embraces Occam's Razor, allows for the 'miracles' told in the Bible, and also gives credence to God transcending His dimensionality to stoop in love limiting Himself to our dimensions, and to be among us...to offer us a Rescue plan. How many times...in the movies...have we tried to invent a time machine (some contraption that is frankly, animistic) which is really quite a silly machine or box or gate? We have so much trouble with time and yet we also seem to have eternity written into our hearts...as if we are going to live forever and so it is by that 'information' that leads us to entertain time travel...to contemplate such a possibility...in the movies. What if we are foreigners here, that this is not our home (our dimensionality limitation) and that each one of us is like a spirit in an earthsuit (as is an astronaut in a spacesuit)? What if each of us WILL graduate life through death and come out the other side--believe it or not and like it or not!? What if God does not make junk...and the spirit that He gave out (that makes you, you and not me) WILL go back to Him who gave it?! If there is no credence to these thoughts then why should anyone be able to speak them or write them" Well, no more credence than those who entertain time machines in the movies and how many 'things' that we thought up IN the movies came to fruition in the future?
WHERE WOULD HE BE? well, that's not a viable question because we are trying to limited Him by the parameters of a materialist condition of 'where' (remember He is not limited by what we are so space...length, width, and depth)! That by which He created he cannot be limited by anymore than an author of a book must be limited by the plot and characters he developed. Circular references is no more allowed for us than it would be for God--ya can't do brain surgery on your own brain!
WHAT WAS GOD DOING BEFORE THE BIG BANG? Again God is not restricted to time...being 'outside' of it He would be the only uncaused cause and so He would never know not being.
WHO CREATED GOD? God is not restricted to time that is why He told Moses "I AM". God has never known not being not will He ever know such a condition--he is outside of the affects of entropy (Time's Arrow). The second Law of Thermodynamics is not in His dimensionality!
If we are in the remotest created "in His Image" and have any traits that smack oddly in this world as compared to the other creatures that 'live' here then we should introspect...a LOT...before we too fall out of our earthsuit! It is here that change is made (not later...when there is no later to have the time to make the change). Outside of time your spirit will be what it is...made into here; for where there is no time there can be no entropy and therefore no change! If life is to mean anything to us (as we ferret material and selfish gain) it is that we are to seek the Truth of God and know His plan for us in Christ! Again Pascal's Wager bubbles to the top for any recognition of what God has done for us is better than none...God being the supreme lover stooped to conquer in love and we need to know this NOW (before there is no now later)!
What is great is that God does NOT require us to not do science in fact he commands us to seek, and to ask questions, and to reason together, and to test everything (holding on to the good or truth). Science is not God's enemy...we are our own worst enemy! Do more science and figure this out using ALL the methods at our disposal that God has put before us!