MATT STRASSLER
Of Particular Significance

Tag: astronomy

New Webpage Posted: A Core Effect of Quantum Physics

A central issue in discussions of particle physics’ present and future is known as the hierarchy puzzle. Although I discuss the hierarchy — its confusing nature and the debates that it generates — in my upcoming book, I do so rather briefly, and so, I’ll be putting up some new pages on this website with supplemental information. The same information is relevant for the cosmological constant problem. (Older pages already giving various perspectives on these issues can be found here, here and here.)

I have just posted the first new page, on “zero-point motion” and “zero-point energy.” It begins with a verbal, non-technical description of zero-point motion and zero-point energy. There follows a sketch of the details using pre-university math. Future pages will apply these ideas to quantum fields, addressing notions of “vacuum energy density” and the “cosmological constant”, and then turning to “Higgs feedback” and the core of the hierarchy puzzle.

A quick description of the hierarchy in question: it is a hierarchy of energy scales, or of mass scales. One way it can be described is in terms of particle masses:

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POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON February 13, 2024

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Estimating the Distance to Jupiter in My Backyard

Last night, using the methods I described as part of my check-it-yourself astronomy series, I estimated the distance to the planet Jupiter using nothing more than my eyes, a protractor, and a simple calculator. It took about 30 seconds of measuring something before and after sunset, and about 15 more seconds using my cell phone’s calculator. You can do it too, if you have clear skies over the weekend.

There are only two parts of the process:

  1. know which week to ask the question, and
  2. during that week, measure the angle A in the sky between the Sun and Jupiter.
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POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON February 9, 2024

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About the Future Circular Collider (FCC)

A number of people have asked me my opinion concerning CERN‘s proposal for a new, larger and more powerful particle physics collider… or rather, two completely different colliders that would operate in the same tunnel:

  • Phase 1 (two to three decades from now): an electron-positron collider targeted at the detailed physics of Higgs bosons, Z bosons, W bosons and top quarks, using them to search for subtle high-energy phenomena and for rare but dramatic low-energy phenomena;
  • Phase 2: (five to six decades from now) an exploratory proton-proton collider, like the Large Hadron Collider [LHC] but with a higher collision energy, and therefore capable of making discoveries of particles that either have higher mass or a lower production rate than what LHC can handle.
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POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON February 6, 2024

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How “Shooting Stars” Measure the Distance to the Sun

(This is the fourth post in a series, though it can be read independently; here are post #1 , post #2 , and post #3.)

For many years, I thought that measuring the distance to the Sun was quite difficult for a non-astronomer. I had the impression that it requires precision measurements, often involving telescopes or information from satellites, and that it was only easy to obtain a minimum distance and a maximum distance that were still quite far apart, as I explained in my last post.

But it’s not true. As I’ll explain today, it turns out that anyone can estimate the distance to the Sun, at night, with nothing more than the naked eye, basic reasoning, and… meteors.

Just from the fact that a long meteor crosses the sky in a few seconds, you can infer that the Earth-Sun distance is something like 100 million miles (km). If the Sun were only 10 million miles (km) away, the meteors would lazily drift among the stars, only a bit faster than the motions of the space station and other satellites, which take minutes to cross the sky. Meanwhile, if the Sun were a billion miles (km) away, then meteors would flash across the sky in a fraction of a second.

With a little more work and knowledge, you can use meteors to make an estimate of the Sun’s distance that’s well within a factor of 2 of the truth. It’s not even that hard to get a precise measurement that’s good to 10% or so.

It may seem odd that one can use such little specks of dust in the Earth’s atmosphere to determine, without a telescope, how far it is to the Sun. But in fact the method is simple. It’s so simple that it must have been pointed out two centuries ago. Curiously, though, I’ve never seen it written down anywhere. It seems to be little-known, even to scientists.

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POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON January 23, 2024

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How Far Could the Sun Possibly Be?

(This is the third post in a series, though it can be read independently; here are post #1 and post #2; and post #4 blows this one out of the water, so don’t miss it!)

Measuring the distance to the Sun is challenging, for reasons explained in my last post. Long ago, the Greek thinker Aristarchus proposed a geometric method, which involves estimating the Moon’s sunlit fraction on a certain date. Unfortunately, because the Sun is so far away, his approach isn’t powerful enough; Aristarchus himself underestimated the distance. [This last remained true for later astronomers before the 17th century, though they got closer to the truth, presumably by using more precise methods than you or I could easily apply. I doubt anyone truly found a maximum possible distance to the Sun just using geometry.] The best we can do, using Aristarchus’ method and our naked eyes, is determine a minimum possible distance to the Sun: a few million miles.

Figure 1: A simple application of Aristarchus’ method tells us that the minimum distance to the Sun is a few million miles (km), ruling out the red region. But the entire green region is still allowed.

Today we’ll see how to obtain a maximum distance to the Sun, using an approach suggested in the previous post: by measuring speeds. Specifically, we’ll make use of a speed that the ancient astronomers weren’t aware of: the speed of light, also known as the cosmic speed limit c. That’s 186,000 miles (300,000 km) per second, or 5.9 trillion miles (9.5 trillion km) per year. We’ll find the Sun’s distance is less than 12 billion miles… still much larger than its true distance, but a significant improvement on our starting point!

Figure 2: By the end of this post, we’ll know a maximum possible distance for the Sun, too.
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POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON January 19, 2024

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Why is it So Hard to Measure the Distance to the Sun?

(This is the second post in a series; here’s post #1.)

It’s not too hard to measure the distance to the Moon; the Greeks did it over two thousand years ago. First you measure the size of the Moon, which can be done in various ways; for instance, you can use the occultation (i.e. blocking) by the Moon of a star or planet, or the outer edges of a solar eclipse, as viewed in different locations on the Earth. These measurements do require multiple people at different locations to accurately report what they have witnessed, but they don’t require any fancy equipment or highly precise observations. Then you can quickly determine the distance to the Moon using the angular diameter of the Moon on the sky.

However, measuring the distance to the Sun, or to any other planet, is much more difficult. Today I’ll explain why… and this will help us envision a way around the problem.

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POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON January 17, 2024

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