Did Hubble formulate his constant by observing space time?
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answers:
Raymond say: No one can observe "spacetime" as it is a mathematical construct combining space and time. Great for formulas, but it does not exist as an object to observe. The best analogy I can find is: you can observe the altitude of a plane by observing the plane and the ground. You cannot observe an object called "altitude".
Hubble and Lemaitre worked the constant by observing the apparent recession rate of galaxies. They had found that the rate of recession was proportional to the apparent distance of the galaxy.
They divided the rate of recession by the distance in order to find this "constant".
What they found led them to believe (at the time) that the universe was something like a half-a-million years old (still a lot more than what had been assumed, up to then).
Father Lemaitre (yes, he was a priest) then assumed that something happened at that first moment to cause all these galaxies to fly away from each other (The Primeval Atom Hypothesis, 1927).
If it only with Father Lemaitre's mathematical model (early 1930s) that we can talk of space itself expanding (translation = it is not the galaxies that are flying apart, but the amount of space between them that keeps increasing -- it is space itself that is expanding). It is that model that eventually became the Big Bang theory (but that is a different story).
From that time, the rate of expansion of space (now estimated to be around 70 km/s per Megaparsec of distance) has been refined many times, but it has continued to be called "Hubble's constant", AS IF the value was a well-known constant value (we already know that, at some times like "inflation", it was not constant).
Lately (last 20 years) some evidence shows that this rate MIGHT be increasing -- much to the surprise of all cosmologists (up to then, the debate was about the rate at which it should be slowing down).
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Jeffrey K say: Yes. Hubble's constant describes the expansion of the universe, as observed by astronomers.
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Ronald 7 say: More or less
As the case may be
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tham153 say: he observed the Doppler shift indicated speed of galaxies moving away, and plotted this on a graph against apparent magnitude
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Nyx say: Nope. By looking at the redshifts of galaxies that are at different distances.
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Tom S say: The observations he used were of the red-shift of distant galaxies, mostly acquired by others.
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hoarseman say: Just space
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Raymond say: No one can observe "spacetime" as it is a mathematical construct combining space and time. Great for formulas, but it does not exist as an object to observe. The best analogy I can find is: you can observe the altitude of a plane by observing the plane and the ground. You cannot observe an object called "altitude".
Hubble and Lemaitre worked the constant by observing the apparent recession rate of galaxies. They had found that the rate of recession was proportional to the apparent distance of the galaxy.
They divided the rate of recession by the distance in order to find this "constant".
What they found led them to believe (at the time) that the universe was something like a half-a-million years old (still a lot more than what had been assumed, up to then).
Father Lemaitre (yes, he was a priest) then assumed that something happened at that first moment to cause all these galaxies to fly away from each other (The Primeval Atom Hypothesis, 1927).
If it only with Father Lemaitre's mathematical model (early 1930s) that we can talk of space itself expanding (translation = it is not the galaxies that are flying apart, but the amount of space between them that keeps increasing -- it is space itself that is expanding). It is that model that eventually became the Big Bang theory (but that is a different story).
From that time, the rate of expansion of space (now estimated to be around 70 km/s per Megaparsec of distance) has been refined many times, but it has continued to be called "Hubble's constant", AS IF the value was a well-known constant value (we already know that, at some times like "inflation", it was not constant).
Lately (last 20 years) some evidence shows that this rate MIGHT be increasing -- much to the surprise of all cosmologists (up to then, the debate was about the rate at which it should be slowing down).
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