# I Who really found out the Universe's acceleration?

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1. Jul 19, 2016

### Phys12

Prof. Brian Schmidt got the Nobel Prize for his work in expansion of the universe which he did in 1998. His team was able to figure out that earlier in the past, the universe's expansion rate was slower than it is right now and it's actually increasing day by day.

However, wasn't the same thing given by Edwin Hubble who said that the velocity of a galaxy is higher if it's farther away. Doesn't it imply that the universe's expansion is accelerating as did Prof. Schmidt's study? What new did Prof. Schmidt and his team really discover?

2. Jul 19, 2016

### DrSteve

Please recall that this is not projectile motion under the influence of gravity; rather the expansion of space. The expanding balloon or raisin bread are commonly used analogies.

Hubble found a linear relationship between velocity and distance; Schmidt et al found a non linear relationship between these two variables.

3. Jul 19, 2016

### Chronos

Einstein may have been credited for discovering both expansion and accelerated expansion had he taken his original calculations more seriously.

4. Jul 20, 2016

### Phys12

So, Hubble found that as the distance increased, the velocity increased. So, if you were to plot a graph between distance and velocity, it'll be a straight line. However, Prof. Schmidt's work got an exponential line in the graph, correct?

5. Jul 20, 2016

### DrSteve

The relationship is not linear, but not exponential, either. There is no simple functional form for the general relationship.

6. Jul 20, 2016

### Phys12

But the basic idea is the same, right? Edwin Hubble got one that said that velocity of galaxies increases as a function of distance, while Brian Schmidt said that the velocity accelerates. So, Edwin Hubble expanded the universe like a balloon at a uniform rate, while Brain Schmidt increased the volume of space added per second to the ballon.

7. Jul 20, 2016

### DrSteve

Just to be clear, in both cases space is itself expanding (crudely speaking, new space is being created each second), but in the accelerating universe this newly created space itself contains a little energy (the cosmological constant) that in turn modifies how much space is being added each second. So it is intrinsically non-linear.

8. Jul 20, 2016

### Phys12

All right, thanks! :)