Lok said:Thanks for your reply.
Is it not possible to see if expansion is still happening by time lapse? Has this been done?
Would comparing the redshift of a Gravitationally lensed system be possible? I mean where in one path the light travels a few hundred years more.
I ask these as evidence besides redshift for an expanding universe is scarce on wiki and the internet. And redshift is just the speed at a past point. There is nothing in it to say that this acceleration did not just dim away and all we see is the past image of it.
Nice analogy. Yet if the Suns disappearance is gradual over an hour or so. With the difference in light intensity of one minute we can statistically predict it's demise.phinds said:There is also, in exactly the same way, no evidence whatsoever that the sun did not disappear 1 minute ago and we just haven't noticed yet and won't for another 7 minutes.
Hey, Chronos. I thought the rate of expansion was 1/144th of a percent per million years? Shouldn't it then take 144 million years to obseve a 1% increase in distance?Chronos said:Our redshift measurement uncertainty is no less than 1%, at best. Using a naïve approach, the CMB [z~1089] as our test subject, and Jorrie's cosmological calculator, http://www.einsteins-theory-of-relativity-4engineers.com/cosmocalc_2013.htm, the time required for a 1% change in distance at z~1089 is 6361 years. It would take a VERY long time to detect any measurable change in the CMB redshift.
Lok said:Nice analogy. Yet if the Suns disappearance is gradual over an hour or so. With the difference in light intensity of one minute we can statistically predict it's demise.
That applies to the current Hubble flow [H0]. I used the CMB at z~1089 to illustrate how long it takes to notice any difference even when the Hubble flow was enormous compared to the present. If you plug in z=0 to Jorrie's calculator you will note the time required for a 1% growth in cosmic distance is ~140 million years.Bandersnatch said:Hey, Chronos. I thought the rate of expansion was 1/144th of a percent per million years? Shouldn't it then take 144 million years to obseve a 1% increase in distance?
The primary evidence for the expansion of the universe comes from observations of the redshift of light from distant galaxies. This redshift indicates that the galaxies are moving away from us, and the farther away a galaxy is, the faster it appears to be moving. This is known as Hubble's Law and provides strong evidence for the universe's expansion.
Scientists use a variety of methods to measure the expansion of the universe, including the aforementioned redshift of light from distant galaxies, observations of the cosmic microwave background radiation, and the use of standard candles, such as supernovae, to determine the distance of faraway galaxies.
No, the expansion of the universe is not constant. In fact, it is believed that the expansion is accelerating, meaning that the rate of expansion is increasing over time. This discovery was made through observations of distant supernovae and has been confirmed by other methods, such as measurements of the cosmic microwave background radiation.
Based on current observations and theories, it is unlikely that the expansion of the universe will ever stop. In fact, it is believed that the expansion will continue forever, with galaxies becoming increasingly more distant from each other. This is due to the presence of dark energy, a mysterious force that is thought to be driving the acceleration of the expansion.
The discovery of the expansion of the universe has had a profound impact on our understanding of the universe. It has led to the development of the Big Bang theory, which states that the universe began with a single, incredibly dense and hot point and has been expanding ever since. It has also raised questions about the ultimate fate of the universe and the role of dark energy in its expansion.