# Earth's Hubble velocity and measuring Hubble at large distances

• B
• Nick Levinson
In summary, scientists are unsure of how fast Earth is moving through the universe because they can't figure out the Hubble constant using currently available technology. They might be able to measure the speed of Earth using instrumentation but if the direction of the Hubble movement differs, they would need to measure multiple points to calculate the speed.
Nick Levinson
TL;DR Summary
Can we infer the Hubble speed even if we don't know where the center of the known universe is?
Just curious.

We can't figure out Earth's speed of travel through the universe due to the Hubble constant because that would be measured from the center of the universe and the center is located somewhere unknown to us except that it is beyond what we can perceive, i.e., more than about 63 Gly (billion light-years) away. I gather we have no generally accepted scientific hypothesis positing a center at a more specific locus.

Couldn't we estimate the Hubble speed anyway? Suppose we observe (through instrumentation) in one direction a point at a known far distance, say, 30 Gly, measure the Hubble speed and direction there, look in the opposite direction an equal distance, measure the Hubble speed and direction there (presumably the direction would be the same), and use that data to calculate the Hubble speed at Earth and the locus of the center of the known universe, which is where the Hubble speed is zero. If we measure but find that the directions of Hubble movement differ, I suppose we could measure at three points and calculate, if that isn't too complicated.

The speed without the Hubble constant is about 2.5 million miles per hour, at moments when everything is moving in the same direction, as if an observer is on the Equator facing forward as the planet turns on its axis while facing forward as the planet goes around the sun while facing forward as the Solar System moves through the Milky Way and so on. I'd add the Hubble-derived minimum speed to the 2,500,000 MPH to yield an estimated total velocity.

I guess something is wrong with my procedure or it would have been done by now and we’d know the Hubble speed at Earth. Where’s my error? Or is it right but so expensive to do that we haven’t yet?

The (main) error is that there is no centre of the universe in any of the mainstream models, so no wonder nobody's looking.

PeroK
berkeman
The question in my summary in the opening post was not one I had asked in the thread of over three years ago.

Since it was three years, I thought the corpus of the science might have been updated with discoveries. So I asked.

Motore
Nick Levinson said:
Since it was three years, I thought the corpus of the science might have been updated with discoveries. So I asked.
You think that newer science will redefine what the observable universe is? Dream on.

I didn't say "will". I said "might".

I think Stephen Hawking once said there is nothing major left to discover, and he was smat, recent, and academically respected, but that kind of claim has been made for decades by various authorities and, except for the most recent claims, has been proven wrong every time before. Three years may be short, but both science and technology are developed by people who do indeed make discoveries, such as of branches of math, and schedules are not fixed. Einstein added to what Newton found. If you believe that you get an education and then there's nothing new after that, revise that. Human knowledge hasn't been static yet, sometimes stagnant but not frozen forever.

Even if what we are capable of observing hasn't changed, our appreciation or understanding of it can. And technology is generally behind science for what is possible in the hands of the current humans, and as technological capabilities advance at the edge we might discover something that leads us to reconsider our scientific knowledge. In chemistry, the periodic table provided an intellectual framework that eased discovering more elements.

## 1. How is Earth's Hubble velocity measured?

Earth's Hubble velocity is measured by using the Hubble Space Telescope to observe the redshift of distant galaxies. The redshift is caused by the expansion of the universe, and the greater the redshift, the faster the galaxy is moving away from us. By measuring the redshift of multiple galaxies at different distances, scientists can calculate Earth's Hubble velocity.

## 2. What is the significance of Earth's Hubble velocity?

Earth's Hubble velocity is significant because it is a measure of the expansion rate of the universe. This expansion rate, known as the Hubble constant, helps scientists understand the age, size, and future of the universe. It also provides evidence for the Big Bang theory and the concept of an expanding universe.

## 3. How is Hubble measured at large distances?

Hubble is measured at large distances by using the Hubble Space Telescope to observe the redshift of distant galaxies. The further away a galaxy is, the faster it appears to be moving due to the expansion of the universe. Scientists use this information to calculate the Hubble constant, which is a measure of the rate of expansion of the universe.

## 4. What is the maximum distance that Hubble can measure?

The Hubble Space Telescope can measure distances up to approximately 10 billion light-years away. Beyond this distance, the expansion of the universe causes the light from galaxies to be stretched to the point where it becomes undetectable by current technology.

## 5. How accurate is Hubble's measurement of the Hubble constant?

The accuracy of Hubble's measurement of the Hubble constant has improved over time as technology has advanced. Currently, the uncertainty in the Hubble constant is around 2.4%, meaning that the value could be off by that amount in either direction. However, ongoing research and advancements in technology continue to improve the accuracy of this measurement.

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