Industries in Depth

The visible universe might be smaller than we thought

A composite of separate exposures taken in 2003 to 2012 with Hubble's Advanced Camera for Surveys and Wide Field Camera 3 of the evolving universe is shown in this handout photo provided by NASA, June 3, 2014.  Researchers say the image, from a new study.

There's a 13.8-billion-light-year radius marking the edge of what mere mortals could see. Image: NASA

Dave Mosher
Science and Technology Correspondent, Business Insider
Our Impact
What's the World Economic Forum doing to accelerate action on Industries in Depth?
The Big Picture
Explore and monitor how Space is affecting economies, industries and global issues
A hand holding a looking glass by a lake
Crowdsource Innovation
Get involved with our crowdsourced digital platform to deliver impact at scale
Stay up to date:


The visible universe just shrunk by 320 million light-years in all directions, updating a famous calculation that physicists first made 13 years ago.

If you're trying to calculate the size of the cosmos, the speed of light — the fastest anything can go — is a tempting place to begin and end. You'd reason that since the Big Bang happened some 13.8 billion years ago, there's a 13.8-billion-light-year radius marking the edge of what mere mortals could see.

Not so.

As physicists have shown again and again over the past century, space is expanding faster and faster. There's also a blinding glow of light that didn't clear up until about 378,000 years after the Big Bang — an event called recombination (when particles finally cooled down enough to form the first atoms).

If you take expansion, recombination, and other variables into account, as physicist J. Richard Gott III and several of his colleagues did in 2003, you get an observable universe that's roughly 45.66 billion light-years in radius — or 91.32 billion light-years wide (if diameter is your thing).

However, as physicists Paul Halpern and Nick Tomasello at the University of the Sciencesexplain in a post on, that calculation was based on data from the WMAP satellite, which mapped the afterglow of the Big Bang — and that data is no longer the best around.

Swapping in newer, more refined data on the universe's expansion from the European Space Agency's Planck satellite, Halpern and Tomasello calculated that the observable edge of the universe is actually 0.7% smaller, or 45.34 billion light-years in radius.

Their paper with the new number-crunching will appear in an upcoming edition of the journal Advances in Astrophysics.

"A difference of 320 million light-years might be peanuts on the cosmic scale, but it does make our knowable universe a little bit cozier," Tomasello wrote in the post.

A few things could stretch this observable limit a bit to 46.31 billion light-years, though — namely ghostly particles called neutrinos.

Neutrinos pass through ordinary matter as if it isn't there, so they could have sailed right through the glow of recombination and may offer the earliest-ever view of the universe. But the same reason they could do that also makes them devilishly hard to detect, as any physicist with an underground neutrino-detecting laboratory can attest.

Don't miss any update on this topic

Create a free account and access your personalized content collection with our latest publications and analyses.

Sign up for free

License and Republishing

World Economic Forum articles may be republished in accordance with the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Public License, and in accordance with our Terms of Use.

The views expressed in this article are those of the author alone and not the World Economic Forum.

World Economic Forum logo
Global Agenda

The Agenda Weekly

A weekly update of the most important issues driving the global agenda

Subscribe today

You can unsubscribe at any time using the link in our emails. For more details, review our privacy policy.

Deep dive: Everything you need to know about industry transformation at #AMNC24

Pooja Chhabria

June 23, 2024


About Us



Partners & Members

  • Join Us

Language Editions

Privacy Policy & Terms of Service

© 2024 World Economic Forum