Friday, September 30, 2016

Colonizing the universe

Retired mathematical physicist Freeman Dyson writes:
When humans begin populating the universe with Noah’s Ark seeds, our destiny changes. We are no longer an ordinary group of short-lived individuals struggling to preserve life on a single planet. We are then the midwives who bring life to birth on millions of worlds. We are stewards of life on a grander scale, and our destiny is to be creators of a living universe. We may or may not be sharing this destiny with other midwife species in other parts of the universe. The universe is big enough to find room for all of us.
Some ppl are ready to go:
Elon Musk is preparing to reveal further details of his hugely ambitious plan to build a city on the surface of Mars.

Tomorrow, the billionaire’s SpaceX is holding an event called “Making Humans An Interplanetary Species” which will shed light on the Red Planet exploration scheme.

Ahead of the event, Musk shared images of a new rocket booster called the Raptor, which will power an “Interplanetary Transport System”.

His firm has carried out a test-firing of the device, which is designed to propel a spaceship all the way to the Red Planet.
But even Dyson does not believe in quantum gravity.

Cosmologist Lawrence M. Krauss wrote last year:
How can we tell if gravity is quantum?

Freeman Dyson, who is a brilliant physicist and a contrarian, he had pointed out based on some research — he’s 90 years old, but he had done some research over the years — I was in a meeting in Singapore with him when he pointed out that we really don’t know if gravity is a quantum theory. Electromagnetism is a quantum theory because we know there are quanta of electromagnetism called photons. Right now they’re coming, shining in my face and they’re going into the camera that’s being used to record this and we can measure photons. There are quanta associated with all of the forces of nature. If gravity is a quantum theory, then there must be quanta that are exchanged, that convey the gravitational force; we call those gravitons. They’re the quantum version of gravitational waves, the same way photons are the quantum version of electromagnetic waves. But what Freeman pointed out is that there’s no terrestrial experiment that could ever measure a single graviton. He could show that in order to build an experiment that would do that, you’d have to make the experiment so massive that it would actually collapse to form a black hole before you could make the measurement. So he said there’s no way we’re ever going to measure gravitons; there’s no way that we’ll know whether gravity is a quantum theory.

What I realized, and Frank and I codified in our paper, is that actually the universe acts like a graviton detector, in [the] sense that processes in the early universe produced phenomena that could be observed today as gravitational waves. But those events, those processes, will only work if gravity is a quantum theory. If gravity isn’t a quantum theory, we won’t see these gravitational waves from the very early universe, which BICEP thought they saw. Now BICEP may not have seen gravitational waves from the early universe, but the fact that we recognize that if this phenomena called inflation happens in the very early universe, and if it produces gravitational waves, that will tell us that gravity is a quantum theory; therefore, all of the problems of quantum gravity will need to be addressed by theorists, giving job security for generations.
Dyson is right here, and all the talk about quantum gravity is unscientific speculation.

1 comment:

  1. Roger, you are forgetting that deep space travel is impossible from an energy standpoint. Even optimistic assumptions with the relativistic rocket equation require enormous amounts of energy that would quickly exhaust the entire earth. Notice that we can barely communicate with deep space satellites with turbo code, MIMO, BPSK etc... within the solar system. Large attenuation!