Best Examples of Simulating the Expansion of the Universe with Balloons

Starting with simple, visual examples of simulating the expansion of the universe with balloons

When teachers and students talk about examples of simulating the expansion of the universe with balloons, they’re usually thinking of the classic setup: you draw dots on a balloon, then blow it up to show how galaxies move away from each other as space expands.

That basic idea is still one of the best examples because it nails the big-picture concept: galaxies aren’t flying through space like bullets; instead, space itself is stretching, and galaxies go along for the ride.

Let’s build on that classic model in several directions, so you have multiple examples of simulating the expansion of the universe with balloons that can work for different grade levels and science fair ambitions.

Example of a classic galaxy expansion balloon (with real measurements)

In this first example of simulating the expansion of the universe with balloons, you’ll turn a quick classroom demo into a real experiment with data.

You’ll need:

• 1 latex balloon (light color so you can see markings)
• Permanent marker
• Flexible measuring tape or a piece of string and a ruler
• Notebook or spreadsheet

Step-by-step idea:

Start with the balloon only slightly inflated and tied. Mark 6–10 small dots scattered around the surface. Each dot is a “galaxy.” Choose one dot to be your “home galaxy” and label it H. Measure the distance from H to each other dot in centimeters. Then, gently inflate the balloon a bit more and re-measure those distances.

You now have:

• Initial distances (before expansion)
• Final distances (after expansion)
• Change in distance for each galaxy

What you’ll notice is that galaxies that started farther away from H have larger increases in distance. That mirrors how astronomers measure the expansion of the universe: distant galaxies appear to recede faster than nearby ones, a pattern described by Hubble’s Law. NASA has great background explanations on this at https://science.nasa.gov/universe/galaxies/.

This is one of the best examples of simulating the expansion of the universe with balloons because you’re not just watching the balloon grow; you’re collecting data and seeing a real pattern.

Advanced example: mapping “Hubble’s Law” with a balloon

If you want to push this further for a science fair, you can turn your measurements into a graph that looks a lot like what astronomers use.

In this example of simulating the expansion of the universe with balloons, you:

• Use the same balloon and galaxy dots from the previous activity.
• Record the initial and final distances for each galaxy.
• Calculate how much each distance changed.
• Then plot a graph with:
  • Horizontal axis: initial distance from H (in cm)
  • Vertical axis: change in distance after inflation (in cm)

You’ll probably see a trend: the farther a galaxy starts, the more its distance increases. That’s the balloon version of Hubble’s Law: speed is proportional to distance.

To connect this to real astronomy, you can read about the real Hubble constant and galaxy redshifts on resources like:

• NASA’s HubbleSite education pages: https://hubblesite.org
• The National Radio Astronomy Observatory education pages: https://public.nrao.edu

Cite those sources in your project report to show that your balloon graph is mimicking actual observational data.

Examples include surface vs. inside: correcting the “center of the universe” myth

One of the most helpful examples of simulating the expansion of the universe with balloons is a version that fixes a common misunderstanding: people often think the universe is expanding from a central point, like an explosion.

The balloon model is better if you focus on the surface of the balloon, not the inside. The surface is like the 3D universe we live in (we’re simplifying a bit here), and the center of the balloon doesn’t represent anything real.

Try this variation:

• Draw galaxies only on one side of the balloon.
• Ask a friend to pick any galaxy and call it the “center.”
• When you inflate the balloon more, every galaxy sees all the others moving away, and it looks like each one could be the center.

This gives you one of the best examples of simulating the expansion of the universe with balloons for explaining that there is no special center in the standard cosmological model. From every galaxy’s point of view, everything else appears to be moving away.

You can back this up with explanations from university cosmology courses, such as open educational resources from MIT or other universities. A good starting point is MIT’s OpenCourseWare astronomy content: https://ocw.mit.edu.

Comparing different rates of expansion: slow, fast, and accelerating

Modern astronomy tells us that the universe’s expansion is not just happening—it’s accelerating. That’s where dark energy comes in, based on observations of distant supernovae in the late 1990s and refined through the 2000s and 2010s.

You can create examples of simulating the expansion of the universe with balloons that compare different types of expansion:

• A balloon inflated at a steady rate (like a universe with constant expansion)
• A balloon inflated slowly at first, then faster (like an accelerating universe)
• A balloon inflated and then held steady (like a universe where expansion slows and nearly stops)

Here’s a practical way to do it:

Use three similar balloons with the same pattern of galaxy dots. For each one, inflate in stages and record the balloon’s circumference with a measuring tape.

• For balloon A, add the same amount of air each time (steady expansion).
• For balloon B, add a little air at first, then more air with each step (accelerating expansion).
• For balloon C, add air at first, then stop adding and just hold it (expansion that slows and pauses).

By comparing your data tables and simple graphs, you can explain how modern observations, including those from missions like the Planck satellite and large galaxy surveys, support an accelerating universe. A good background resource is NASA’s cosmology overview: https://map.gsfc.nasa.gov/universe/.

A 2D twist: balloon plus stickers and stretchy fabric

If you want more tactile, visual examples of simulating the expansion of the universe with balloons, mix materials.

Try this hybrid setup:

• Use a balloon as before, but instead of drawing galaxies, stick on small paper circles or tiny stickers.
• On a separate day, stretch a piece of elastic fabric (like an old T-shirt or exercise band) on a frame or between two chairs.
• Mark or glue similar “galaxies” on the fabric.

Inflate the balloon and stretch the fabric in stages, measuring distances between galaxies in both models. Then compare:

• The balloon surface is curved, so distances wrap around.
• The fabric is flat, more like the standard “rubber-sheet” model.

This gives you real examples of how cosmologists think about space: it can be flat, curved, or something more exotic. You can mention that current data (as of 2024–2025) suggests the universe is very close to flat on large scales, based on measurements of the cosmic microwave background and galaxy surveys.

Time-lapse example: photographing balloon expansion like a telescope survey

Another strong example of simulating the expansion of the universe with balloons uses time-lapse photos or short videos.

Set up your phone or camera on a stand so it points at the same part of the balloon each time. Draw a cluster of galaxies on that region. Then:

• Take a photo when the balloon is small.
• Inflate a bit, take another photo.
• Repeat a few times.

Later, compare the images side by side. You’ll see that the galaxies get farther apart, but each galaxy keeps its shape and size. That’s an important point: galaxies themselves don’t expand with the universe; gravity holds them together. It’s the space between galaxies that stretches.

You can even trace the positions on transparent paper and measure how the distances change. This is a great way to explain how telescope surveys, like those done by the Sloan Digital Sky Survey (SDSS), map galaxy positions at different distances and build a 3D picture of the universe.

Using color to show redshift: a visual example of galaxy light stretching

The balloon doesn’t just help with distances. It can also give you a visual example of how light from distant galaxies gets stretched, which astronomers see as redshift.

Try this variation:

• Draw galaxies in different colors (blue, green, red) on the balloon.
• As you inflate the balloon, explain that while the drawing doesn’t change color, the idea is that the light waves between galaxies are being stretched, similar to how the space on the balloon stretches.

For a more vivid model, use strips of colored tape or string between galaxies. As the balloon inflates, the strips stretch. You can say: “Imagine these strips are light waves. As the universe expands, the waves get longer, which means the light shifts toward the red end of the spectrum.”

You can support this with information from sources like the National Optical-Infrared Astronomy Research Laboratory (NOIRLab) education pages or NASA’s descriptions of redshift and the expansion of the universe.

Limitations of balloon models (and how to explain them in your project)

Even the best examples of simulating the expansion of the universe with balloons have limits. Judges and teachers love when students point these out.

Some key limitations to discuss:

• The balloon has a center; the universe doesn’t (as far as we know). Explain that the center of the balloon is not part of the model; only the surface matters.
• The balloon has edges; the observable universe doesn’t have a known edge. The surface of the balloon is finite and wraps around; the real universe might be infinite.
• Galaxies on the balloon grow as you inflate it; real galaxies don’t. Gravity and other forces keep galaxies, solar systems, and atoms from expanding.
• The balloon can pop. The universe isn’t expected to suddenly pop like that. Current research discusses possibilities like heat death, big rip, or big crunch, but none of those look like a latex balloon exploding.

By including a short “Limitations of the model” section in your display board or report, you show that you understand that these are examples of simulating the expansion of the universe with balloons, not exact copies of reality.

Turning balloon simulations into a strong science fair project

All these examples of simulating the expansion of the universe with balloons can be combined into a full project with a testable question. Here are a few directions you could take:

• Question about rates: How does the rate of balloon inflation affect the relationship between initial distance and change in distance between galaxies?
• Question about curvature: How do distance measurements on a balloon surface compare with measurements on a flat stretchy fabric? What does that say about curved vs. flat space?
• Question about observation: How well can people interpret expansion from still images vs. time-lapse images of a balloon model?

You can:

• Collect data (distances, times, circumference).
• Graph your results.
• Compare what you see to descriptions of cosmic expansion from sources like NASA or university astronomy departments.

For background reading, the following kinds of resources are helpful:

• NASA cosmology pages for up-to-date explanations of expansion and dark energy
• University astronomy course notes (for example, from Harvard, MIT, or other major universities)
• Public outreach sites from observatories and space agencies

By tying your balloon data to real cosmology research, you show that your project is more than a party trick—it’s a meaningful model.

FAQ: Real examples of simulating the expansion of the universe with balloons

Q: What are some real classroom examples of simulating the expansion of the universe with balloons?
Teachers often use a balloon covered in marker dots or stickers to represent galaxies. They measure distances before and after inflation to show that galaxies move farther apart as space expands. Some classes take photos at each inflation step, then compare them like before-and-after telescope images.

Q: Is there an example of a balloon activity that shows accelerating expansion?
Yes. You can inflate the balloon in stages, adding a little air at first and more air with each step. When you measure how distances change between galaxies, you’ll see that the rate of separation increases over time, similar to the idea of dark energy causing accelerating cosmic expansion.

Q: Why do scientists still use examples of balloon models if they’re not perfect?
Because they’re simple, cheap, and powerful for building intuition. While scientists rely on advanced math and observations, balloon models give students a way to see and measure expansion. As long as you explain their limits, they’re a helpful teaching tool.

Q: Can I use these examples of simulating the expansion of the universe with balloons for a high school science fair?
Absolutely. If you include measurements, graphs, and references to real astronomy research, a balloon-based project can be impressive at the high school level. Focus on a clear question—like how distance relates to apparent speed of recession—and show your data.

Q: Where can I learn more about the real expansion of the universe to cite in my project?
Look at NASA’s cosmology and Hubble resources, as well as astronomy pages from major universities. These sources explain Hubble’s Law, dark energy, and current measurements of the universe’s expansion in student-friendly language.

By using several of these examples of simulating the expansion of the universe with balloons, you can build a project that’s hands-on, visually memorable, and scientifically grounded—exactly the kind of thing that stands out on a science fair table.