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ELI5 Yahaaa

Not the chair, not this page

You Have Never Touched Anything

What you call touch is a force pushing back across a gap that never closes.

Pressing afingertip against atable At the smallest scale,a gap that nevercloses
Something is definitely happening. Contact is not the word for it.

  1. Step 1 of 5

    Every surface is a layer of electrons.

    The table's outer layerelectrons,nothing elseA gap that never closesabout ananometreacrossYour own outer layerelectrons,nothing else
    Two sheets of electrons, approaching and never arriving

    An atom keeps its electrons on the outside. So the outermost thing on your fingertip is a sheet of electrons, and the outermost thing on the table is a sheet of electrons. Those are what approach each other.

  2. Step 2 of 5

    Electrons push each other away, hard.

    Your electronsapproaching theirsRepulsion, rising steeply as the gap closesThe force of your push
    The gap stops shrinking when these two match.

    Like charges repel. Two negatives pushed together resist, and the resistance climbs steeply as the gap shrinks — halve the distance and the push roughly quadruples. Long before the surfaces meet, that push has become overwhelming.

    This is why it takes more force to press harder rather than a fixed effort to make contact — you are compressing a spring that gets stiffer the more you squeeze.

  3. Step 3 of 5

    That push is the entire sensation of touching.

    Electronrepulsionsquashes the skin Nerves report thesquashing aspressure

    Your nerves do not detect arrival. They detect deformation — skin being squashed. The squashing is caused by the repulsion, so what you feel as the solidity of a table is literally an electrical force, reported by nerves as pressure.

  4. Step 4 of 5

    It also explains why solid things are solid.

    Atoms in asolid: mostlyempty spaceEach wrappedin repellingelectronsAnd that isall 'solid'has ever meant

    A table holds a cup up for the same reason your finger cannot pass through it. Nothing about the table is full; atoms are mostly empty space. But the electron layers of the cup and the table cannot occupy the same place, and that refusal is what a surface is.

  5. Step 5 of 5

    So how close does it get?

    A human hairAbout 80,000nanometres wideA red blood cellAbout 7,000nanometresThe touching gapAround 1nanometre — andit stays open

    The gap holds at around a nanometre or less — roughly the width of a few atoms. It is a real distance, it never reaches zero under ordinary pressure, and there is no force in everyday life anywhere near strong enough to close it.

    Under enormous pressure — inside a neutron star, say — electron repulsion does eventually lose. That is exactly what makes such objects so strange.

The short version

Touch is the electrical repulsion between two layers of electrons that never quite meet, and your nerves report that push as the feeling of a solid surface.

Try it yourself

Hold two fridge magnets facing the wrong way and push them together slowly. You can feel a solid-feeling barrier with nothing in it. Touching a table is that, at a much smaller scale.

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