# Tritium Tesseract Makes A Nifty Nightlight

As the cube is to three dimensions, the tesseract is to four. Mortals in this universe find it difficult to contemplate four-dimensional geometry, but there are methods of making projections of such heretical shapes in our own limited world. [Sean Hodgins] was interested in the geometry, and decided to build a tesseract featuring everyone’s favourite isotope of hydrogen, tritium.

The build starts with a 3D printed inner and outer frame, sourced in this case from Shapeways in nylon. Both frames have holes which are designed as a friction fit for off-the-shelf tritium vials. These vials use the radioactive decay of tritium with a phosphor coating to create a dim glow which lasts approximately a decade. With the inner frame held inside the outer with the vials acting as structural supports, the inner and outer surfaces are then fitted with semi-transparent mirrored acrylic, creating a nice infinity effect.

It’s a fun trinket that would be perfect as a MacGuffin in any sci-fi film with a weak plot. [Sean] notes that while the tritium glow is disappointingly dim, the device does make a good nightlight. If you’ve built one and get bored with the hypercube, you can always repurpose your tritium vials into a nuclear battery. Video after the break.

## 27 thoughts on “Tritium Tesseract Makes A Nifty Nightlight”

1. Ostracus says:

“Mortals in this universe find it difficult to contemplate four-dimensional geometry”

Time.

1. I tell you what, I did GR in college, and I can attest to the “difficult to contemplate” bit.

1. Paul says:

My GR professor used to say (when writing 3D matrix operations on the blackboard, and sometimes making mistakes) that odd numbers of dimensions were difficult to deal with. Two is easy. Four is good. Three was difficult.

His brain was clearly wired differently from us mortals.

2. p says:

See: Thomas Banchoff–_Beyond_the_Third_Dimension

3. Buriedcode says:

Geometry. Time isn’t geometrical/spacial dimension :D

1. It can be, if you’re moving fast enough, or near a big enough mass.

2. Canoe says:

Copy&paste of a comment on OP’s youtube:

Are you aware that the tritium in those tubes is bathing you in soft x-rays from Bremsstrahlung radiation that you can only detect with scintillation counter? Speaking as somebody who usd to design Geiger and scintillation counters as well as scintillation spectrometers, I see idiocy like this and just think “Darwin in action”. Genetic damage from radiation is a stochastic phenomenon and the only reason that tritium is allowed for use in safety signals is an arbitrary contrasting of received radiation vs. fire danger and typically these radiation sources are NOT NEAR people because they’re in exit signs that people don’t stay next to for extended periods. This is mind numbing stupidity.﻿

1. neo2121 says:

Can I have what that guy is having? He seems to already be living in a parallel universe and I really want to get some of that interdimensional action.

2. AKA the A says:

1st off – do the low energy X-rays even make it through the cube glass?
2nd – inverse square law…unless he shoves it up his…somewhere…the dose rate will fall below ambient once you’re some distance from it
3rd – he could always enclose it in thick acrylic or polycarbonate or just cast the thing in clear epoxy (lead glass plate is hard to come by and plastics will fine work for low-energy x-rays if thick enough)

3. David S says:

Your comment is mind numbing stupidity. There is no dangerous radiation emitted by these tritium tubes.

4. Paul says:

“…mind numbing stupidity.﻿”
About the same mind-numbing stupidity as watching television. The xray spectrum coming off these tritium tubes is very similar to that from old-skool black & white CRTs, but far less in intensity. Both the tritium tubes and a black & white CRT generate light from smacking a phosphor with 10 to 15 keV electrons. Soft X rays are generated from the deceleration (“Bremsstrahlung”) of those electrons in the phosphor and glass. A tritium vial is 4-5 orders of magnitude less “current” (electrons per second) though (~1 GBq tritium vs. ~10 uA CRT beam current).

I have not run the numbers, but I’m sure a short stroll outdoors in daylight is yields a higher dose of damaging radiation to your skin than a tritium vial in your pocket would.

1. Martin says:

AFAIK the most x-rays in old tube TVs came from the HV rectifier tube, not from the CRT.

1. Paul says:

That may once have been true. But I have not seen a HV rectifier tube in a TV in the last half century. Every CRT (TV, ‘scope, or terminal) I have used since the 60s has had solid state rectifiers (granted, a couple of those were selenium).

3. AKA the A says:

1st off – do the low energy X-rays even make it through the cube glass?
2nd – inverse square law…unless he shoves it up his…somewhere…the dose rate will fall below ambient once you’re some distance from it
3rd – he could always enclose it in thick acrylic or polycarbonate or just cast the thing in clear epoxy (lead glass plate is hard to come by and plastics will fine work for low-energy x-rays if thick enough)

1. Brian says:

No, X-Rays of that energy do not pass through the glass of the tube.

1. Paul says:

Brian, check your intuition. You’re wrong.

The x-ray spectrum of the beta-generated Bremsstrahlung has the familiar characteristic x-ray spectral shape, with energies up to the electron’s peak energy of around 18 keV. There’s no fluence up at that maximum, but there’s plenty down in the 15 keV range and below — many millions of xray photons per second. According to the NIST tables, at 10 keV a millimeter of glass lets through 2% of the x-ray photons. At 15 keV, 30% gets through. And, true, the phosphor also stops a significant fraction, but it produces fluorescent X rays too, so it’s a bit of a wash.

So, sure, the glass stops most of it, but it’s misleading and plain wrong to say “X-Rays of that energy do not pass through”.

The actual deposited energy (dose) to nearby skin is still pretty darned low. But I’d still keep the things away from my ‘nads.

2. Brian says:

The average beta energy of the tritium is 5.7KeV, so the maximum energy of Bremsstrahlung that could produce is 5.7keV. So, no, it is not dangerous and X-rays of that energy do not pass through the glass of the tube or the acrylic box it’s in.

4. ino says:

At \$20 per tube, it makes for a pricey nightlight !

1. Shannon says:

Only if it goes over a certain extremely low number of emissions per second, with the tiny mass of tritium in those vials it shouldn’t be a problem, plus, over time it becomes less of a problem!

1. “Yes officer, but if we give it a few decades this whole problem will blow over so can we skip to the bit where you let me go?”

5. janostman says:

Or a flurorescent filament 3D-printed?

6. Hirudinea says:

How to construct a 4D objects 3D representation via a 2D media, my brain hurts.

7. JCG says:

Hmm, would be cool to make with those led filament thingies. Let’s see what i got laying around

8. Maybe a version that has 365nm UV LEDs inside the inner cube, facing out?

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