<p>In early modern physics, the luminiferous aether (or <ahref="please_to_wijnhaven.html#ethernet">ether</a>) was believed to be an invisible space-filling substance or field that was a transmission medium for electromagnetic or gravitational forces.</p>
<p>Peter Guthrie Tait (1837-1901) was a Scottish mathematical physicist, whose investigations in <ahref="#knotTheory">knot theory</a> contributed to the field of topology as a mathematical discipline. His tabulations of knots with ten <ahref="beetroot_to_ciao.html#sevenBridges">crossings</a>, which became known as the <em>Tait conjectures</em>, arose out of experiments he conducted with William Thomspon (Lord Kelvin) in <ahref="beetroot_to_p_lions_es.html#1867">1867</a> at the University of Edinburgh.</p>
<p>If you like a drink, then a Klein bottle is not a recommended receptacle. It may look vaguely like a bottle, but it doesn't enclose any volume, which means that it can't actually hold any liquid. Whatever you pour "in" will just come back out again as the Klein bottle is an example of a non-orientable surface. It has no "inside" and no "outside", instead, just <em>a</em> side.</p>
<p>The unknot, or <i>torus</i>, is the <ahref="please_to_foshan.html#tait">first type</a> of <ahref="beetroot_to_p_lions_es.html#mathematicalKnots">mathematical knot</a> listed in knot theory. Intuitively, the unknot is a closed loop of rope without a knot in it.</p>
