With reference to gravitational waves, which of the following statements is correct?
1
All gravitational waves are as old as the Big Bang itself.
2
Gravitational waves travel at the speed of sound and squeeze and stretch anything in their path.
3
The first gravitational wave was detected by LIGO only in 2015.
4
Gravitational waves were proposed by Madam Qurie in his General Theory of Relativity over a century ago.